Radon is an odorless, colorless radioactive gas naturally occurring in the earth that can cause lung cancer in humans. It can enter homes through foundations and basements unless steps are taken to prevent it. Radon-resistant homes help minimize this risk by including a radon barrier with a fully sealed foundation and plastic sheet or layer of rigid-foam insulation rated for soil contact carefully taped at the seams under the slab or lining a crawl space. Below the radon barrier, a perforated pipe is laid in a 4-inch layer of crushed rock to collect radon and soil gasses and passively vent them through a solid vent pipe that goes up through the house (concealed inside a wall) and vents out through the roof. An electric junction box is installed in the attic near the vent pipe to power an inline fan to turn this passive venting system into an active system in case the radon is not being adequately exhausted through the passive exhaust pipe.